JP2005080748A - Imaging condition set up method and x-ray ct apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging condition set up method and an X-ray CT apparatus which facilitate the setting of the imaging conditions for carrying out the imaging to match the given purpose by the helical scan. <P>SOLUTION: In the imaging by the helical scan of the X-ray CT apparatus, various imaging conditions are made in tabulation (66) and the candidates for the imaging conditions are extracted according to the order of the age of the patients designated by the users, imaging sites, imaging length and the target of the first priority while the dose for the patients is displayed under the candidates for the imaging conditions (601-607) to allow the adjustment (609) of the dose of the user so that the candidates for the imaging conditions are corrected according to the adjustment of the dose to define the imaging conditions (613). When a plurality of imaging candidates exist for the imaging conditions, the defining of the imaging conditions may be done based on the targets (611) of the next priority designated by the users. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an imaging condition setting method and an X-ray CT (Computed Tomography) apparatus, and more particularly to an imaging condition setting method for an X-ray CT apparatus that performs imaging by a helical scan, and imaging by a helical scan. The present invention relates to an X-ray CT apparatus to be performed.

In an X-ray CT apparatus that performs imaging by helical scanning, an imaging condition is set by a user before imaging is started. Various shooting conditions are set according to the shooting target and purpose. Various parameters such as a tube voltage, a tube current, an X-ray beam thickness, an image slice thickness, a helical pitch, and the like are set one by one by setting the imaging conditions. The patient exposure dose is displayed for the set imaging conditions, and the user can determine whether the imaging conditions are appropriate (see, for example, Patent Document 1).
Japanese Patent Laying-Open No. 2003-79611 (page 8-9, FIG. 6-9)

  In the X-ray CT apparatus as described above, it is necessary to reset the imaging conditions when the exposure dose is inappropriate. However, the imaging conditions including a large number of parameters are reset so that the intended purpose can be achieved. It is not easy. In particular, as the number of detection rows of the X-ray detector becomes multi-row and the cone beam character of the X-ray beam becomes remarkable, the difficulty is doubled.

  In particular, when scanning with a thick beam, the scanning is completed quickly, but the automatic control of the tube current in the body axis direction is rough and the exposure dose increases, so the thickness to select depends on the patient age and examination contents. You need to choose carefully.

  SUMMARY OF THE INVENTION An object of the present invention is to realize an imaging condition setting method and an X-ray CT apparatus that can easily set imaging conditions for performing imaging in accordance with an intended purpose by helical scanning.

  (1) One aspect of the invention for solving the above-described problem is an imaging condition setting method for an X-ray CT apparatus that performs imaging by helical scanning, in which various imaging conditions are tabulated in advance and used. Extracting imaging condition candidates from the table according to the patient's designated child, imaging region, imaging length, and highest priority target, and displaying the patient's exposure dose under the imaging condition candidates, The imaging condition setting method is characterized in that the user can adjust the exposure dose, and the imaging condition is determined by correcting the exposure condition candidate according to the adjustment of the exposure dose.

  (2) Another aspect of the invention for solving the above-described problems is an X-ray CT apparatus that performs imaging by helical scanning, and uses a storage unit that stores various imaging conditions preliminarily tabulated. Display means for extracting candidates for imaging conditions from the table in accordance with the patient's child, imaging region, imaging length, and top priority target designated by the person and displaying the patient's exposure dose under the imaging condition candidates And an adjustment unit that allows a user to adjust the exposure dose, and a determination unit that corrects the exposure condition candidate according to the adjustment of the exposure dose to determine the exposure condition. This is an X-ray CT apparatus.

  The highest priority target is preferably an exposure dose in terms of optimizing the exposure dose. The highest priority target is preferably one of exposure dose, image quality, and imaging speed, from the viewpoint of optimizing exposure dose, image quality, or imaging speed. The exposure dose is preferably expressed by DLP from the viewpoint of optimizing the total exposure dose.

  When there are a plurality of candidates for the photographing condition, it is preferable to determine the photographing condition based on the next priority target designated by the user from the viewpoint of obtaining the optimum photographing condition. The next priority target is preferably different from the highest priority target among the exposure dose, the image quality, and the imaging speed in terms of obtaining optimal imaging conditions.

  It is preferable that the tabled shooting conditions are shooting conditions based on results, which is supported by the results. It is preferable that the tabled imaging conditions are imaging conditions based on simulation, from the viewpoint of enriching the imaging conditions regardless of the actual results.

  In the invention in each aspect described above, various imaging conditions are tabulated in advance, and imaging condition candidates are extracted from the table according to the patient's child, imaging region, imaging length, and top priority target specified by the user. The patient's exposure dose under the imaging condition candidate is displayed, the user can adjust the exposure dose, and the imaging condition candidate is modified according to the adjustment of the exposure dose to set the imaging condition. Therefore, the imaging condition setting method and the X-ray CT apparatus that can easily set the imaging conditions for performing imaging that matches the intended purpose by helical scanning can be realized.

  The best mode for carrying out the invention will be described below with reference to the drawings. Note that the present invention is not limited to the best mode for carrying out the invention. FIG. 1 shows a block diagram of an X-ray CT apparatus. This apparatus is an example of the best mode for carrying out the present invention. An example of the best mode for carrying out the present invention relating to an X-ray CT apparatus is shown by the configuration of the apparatus. An example of the best mode for carrying out the present invention relating to the photographing condition setting method is shown by the operation of this apparatus.

  As shown in FIG. 1, the apparatus includes a scanning gantry 2, an imaging table 4, and an operation console 6. The scanning gantry 2 has an X-ray tube 20. X-rays (not shown) emitted from the X-ray tube 20 are shaped (collimated) into a cone-shaped X-ray beam, that is, a cone-beam X-ray, by a collimator 22 and irradiated to the X-ray detector 24. Is done. The X-ray detector 24 has a plurality of detection elements arranged in an array according to the spread of the X-ray beam. The configuration of the X-ray detector 24 will be described later.

  In the space between the X-ray tube 20 and the X-ray detector 24, an imaging target is mounted on the imaging table 4 and carried in. The X-ray tube 20, the collimator 22, and the X-ray detector 24 constitute an X-ray irradiation / detection device. The X-ray irradiation / detection apparatus will be described later.

  A data collection unit 26 is connected to the X-ray detector 24. The data collection unit 26 collects detection signals of individual detection elements of the X-ray detector 24 as digital data. The detection signal of the detection element is a signal representing the projection of the target by X-rays. Hereinafter, this is also referred to as projection data or simply data.

  X-ray irradiation from the X-ray tube 20 is controlled by an X-ray controller 28. The connection relationship between the X-ray tube 20 and the X-ray controller 28 is not shown. The collimator 22 is controlled by a collimator controller 30. The connection relationship between the collimator 22 and the collimator controller 30 is not shown.

  The components from the X-ray tube 20 to the collimator controller 30 described above are mounted on the rotating unit 34 of the scanning gantry 2. The rotation of the rotating unit 34 is controlled by the rotation controller 36. The connection relationship between the rotating unit 34 and the rotation controller 36 is not shown.

  The operation console 6 has a data processing device 60. The data processing device 60 is configured by, for example, a computer. A control interface (interface) 62 is connected to the data processing device 60. The control gantry 2 and the imaging table 4 are connected to the control interface 62. The data processing device 60 controls the scanning gantry 2 and the imaging table 4 through the control interface 62.

  The data acquisition unit 26, the X-ray controller 28, the collimator controller 30 and the rotation controller 36 in the scanning gantry 2 are controlled through the control interface 62. Note that illustration of individual connections between these units and the control interface 62 is omitted.

  A data collection buffer 64 is connected to the data processing device 60. A data collection unit 26 of the scanning gantry 2 is connected to the data collection buffer 64. Data collected by the data collection unit 26 is input to the data processing device 60 through the data collection buffer 64.

  A storage device 66 is connected to the data processing device 60. The storage device 66 stores projection data input to the data processing device 60 through the data collection buffer 64 and the control interface 62, respectively. The storage device 66 also stores a program for the data processing device 60. When the data processing device 60 executes the program, the operation of this device is performed.

  The data processing device 60 performs image reconstruction using the projection data collected in the storage device 66 through the data collection buffer 64. The data processing device 60 is an example of a reconstruction unit in the present invention. For the image reconstruction, for example, a filtered back projection method or the like is used.

  A display device 68 and an operation device 70 are connected to the data processing device 60. The display device 68 is configured by a graphic display or the like. The operation device 70 includes a keyboard having a pointing device.

  The display device 68 displays the reconstructed image and other information output from the data processing device 60. The operation device 70 is operated by a user and inputs various instructions and information to the data processing device 60. The user operates the present apparatus interactively using the display device 68 and the operation device 70.

  FIG. 2 shows a schematic configuration of the X-ray detector 24. As shown in the figure, the X-ray detector 24 is a multi-channel X-ray detector in which a plurality of X-ray detection elements 24 (ik) are arranged in a two-dimensional array. The plurality of X-ray detection elements 24 (ik) as a whole form an X-ray light receiving surface curved in a cylindrical concave shape.

  i is a channel number, for example, i = 1, 2,. k is a column number, for example, k = 1, 2,. The X-ray detection elements 24 (ik) each have the same column number k and constitute a detection element array. Note that the number of detection element rows of the X-ray detector 24 is not limited to 32 rows, and may be an appropriate number.

  The X-ray detection element 24 (ik) is configured by a combination of, for example, a scintillator and a photodiode. However, the present invention is not limited to this. For example, a semiconductor X-ray detection element using cadmium tellurium (CdTe) or the like, or an ionization chamber type X-ray detection element using xenon (Xe) gas may be used.

  FIG. 3 shows the interrelationship among the X-ray tube 20, the collimator 22, and the X-ray detector 24 in the X-ray irradiation / detection apparatus. 3A is a diagram showing a state seen from the front of the scanning gantry 2, and FIG. 3B is a diagram showing a state seen from the side. As shown in the figure, the X-rays emitted from the X-ray tube 20 are shaped by the collimator 22 into a cone-shaped X-ray beam 400 and irradiated to the X-ray detector 24.

  FIG. 3A shows the spread of the cone-shaped X-ray beam 400 in one direction. Hereinafter, this direction is also referred to as a width direction. The width direction of the X-ray beam 400 coincides with the channel arrangement direction in the X-ray detector 24. (B) shows the expansion of the X-ray beam 400 in the other direction. Hereinafter, this direction is also referred to as a thickness direction of the X-ray beam 400. The thickness direction of the X-ray beam 400 coincides with the direction in which a plurality of detection element rows are arranged in the X-ray detector 24. The two spreading directions of the X-ray beam 400 are perpendicular to each other.

  As shown in FIG. 4, for example, the object 8 placed on the imaging table 4 is carried into the X-ray irradiation space by intersecting the body axis with such an X-ray beam 400. The scanning gantry 2 has a cylindrical structure including an X-ray irradiation / detection device inside.

  The X-ray irradiation space is formed in the inner space of the cylindrical structure of the scanning gantry 2. An image of the object 8 sliced by the X-ray beam 400 is projected onto the X-ray detector 24. The X-ray detector 24 detects X-rays transmitted through the object 8 for each detector row. The thickness th of the X-ray beam 400 irradiated to the object 8 is adjusted by the opening degree of the aperture of the collimator 22.

  In parallel with the rotation of the X-ray irradiation / detection device, the X-ray irradiation / detection device is moved relative to the target 8 by continuously moving the imaging table 4 in the body axis direction of the target 8 as indicated by an arrow 42. Thus, the object 8 turns along a spiral trajectory surrounding the object 8. As a result, a so-called helical scan is performed.

  Projection data of a plurality of views (for example, about 1000) per scan rotation is collected. The projection data is collected by a series of X-ray detector 24 -data collection unit 26 -data collection buffer 64. Hereinafter, the projection data is also referred to as scan data. The projection data of each view is also referred to as view data.

  The operation of this apparatus will be described. FIG. 5 shows a flow chart of the operation of this apparatus. As shown in the figure, shooting conditions are set on a stage 501. Details of the shooting condition setting will be described later.

  Next, a helical scan is performed on the stage 503. The helical scan is performed by the scanning gantry 2 and the imaging table 4 according to the imaging conditions set on the stage 501. Next, image reconstruction is performed at stage 505. Image reconstruction is performed by the data processing device 60. The data processing device 60 reconstructs an image by a filtered back projection method or the like based on the projection data collected by the helical scan. The reconstructed image is displayed and stored at stage 507. An image is displayed by the display device 60. The storage of the image is performed by the storage device 66.

  FIG. 6 is a flowchart for setting the shooting conditions. As shown in the figure, at stage 601, adult / infant, age, and anatomy are input. These inputs are made through the operation device 70 by the user. The same applies to the following inputs. Depending on whether the patient is an adult or an infant, an adult input or an infant input is made and its age is input. In addition, a desired imaging region such as a head, an eyeball, a neck, a chest, an abdomen, and a leg is input by an anatomy input.

  Next, on the stage 603, positioning scan and start / end position input are performed. The positioning scan is performed by moving the imaging table 4 in the body axis direction of the patient while irradiating the patient with X-rays while the rotation of the scanning gantry 2 is stopped. This provides a fluoroscopic or scout image of the patient. In addition, an average X-ray dose for each position in the body axis direction for automatic tube current control (automilliampere: auto mA) is obtained. The start / end position input is performed by the user inputting a start position and an end (end) of the helical scan using a fluoroscopic image. The shooting length by helical scan is determined by inputting the start / end position.

  Next, at stage 605, the highest priority target is input. The highest priority target is the highest priority target for imaging of the patient. For example, for a patient with a low tolerance of exposure dose such as a child, the highest priority is given to making the exposure dose as small as possible. On the other hand, for patients with a relatively large tolerance of exposure dose such as adults, image quality or imaging speed may be given the highest priority over exposure dose. Hereinafter, the exposure dose is also referred to as “dose”, the image quality is also referred to as “IQ (image quality)”, and the imaging speed is also referred to as “speed”.

  As the highest priority target, for example, any of dose, IQ, and speed is input. The input of the dose is performed, for example, by inputting a DLP (Dose Length Product) numerically. Alternatively, the input of dose priority is performed in the sense of making the dose as small as possible. With regard to IQ and speed, an input of IQ priority is performed in the sense of improving the IQ as much as possible, and an input of speed priority is performed in the sense of improving the speed as much as possible.

  Next, at stage 607, the imaging condition candidate extraction and DLP display are performed. The photographing condition candidate extraction and the DLP display are performed by the data processing device 60. The data processing device 60 extracts candidates for shooting conditions according to adult / infant, anatomy, shooting length, and top priority target from the shooting condition table stored in the storage device 66 in advance, and shooting is performed under those conditions. The DLP when it is supposed to be displayed is displayed.

  This DLP is a so-called default DLP. When there are a plurality of shooting condition candidates, all of them are extracted, and a default DLP is displayed for each of them. Display of the shooting condition candidates and the default DLP is performed on the display device 68.

  The imaging condition table is a table of various imaging conditions, and there are various combinations of parameters regarding tube voltage, tube current, beam thickness, helical pitch, slice thickness of the reconstructed image, image reconstruction filter, etc. It is a table. The tube current is stored in the form of a current profile in the body axis direction obtained by a positioning scan in advance according to the amount of X-ray transmission in the body axis direction of the patient. The current profile is finer as the beam thickness is thinner and rougher as the beam thickness is thicker. A fine profile is more effective in reducing dose than a rough profile.

  Such a shooting condition table is formed by, for example, a compilation of past shooting results. Or you may form by simulation (simulation) of various imaging | photography conditions.

  Next, DLP adjustment is performed on the stage 609. The DLP adjustment is performed by the user. Since the default DLP may be larger than the desired DLP, in such a case, the user adjusts the displayed DLP through the operating device 70 so that the displayed DLP becomes a desired value. Along with this DLP adjustment, the data processing device 60 corrects the extracted shooting conditions so that the DLP matches the adjusted DLP. The imaging condition is corrected, for example, by reducing the overall amplitude of the tube current profile. When the default DLP is equal to or less than the desired DLP, the DLP adjustment is not performed, and therefore the photographing condition is not corrected.

  Next, at stage 611, the next priority target is input. The next priority target is entered by the user. The next priority target is a target prioritized next to the highest priority target, and a target that has not been set as the highest priority target among dose, IQ, and speed is input. Thus, for example, if dose is the highest priority target, IQ or speed is input as the next priority target. These are input as IQ priority or speed priority. The input of the next priority target can be omitted depending on the case.

  Next, at the stage 613, the optimum photographing condition is extracted. Optimal photographing condition extraction is performed by the data processing device 60. The data processing device 60 extracts a shooting condition that matches the next priority target from the shooting condition candidates. As a result, the optimum shooting condition is extracted from the shooting condition candidates.

  In this way, after entering adult / infant, anatomy, and start / end, the optimum shooting conditions are automatically set simply by entering the highest priority target and (if necessary) the next priority target. Therefore, it is not necessary to input each parameter constituting the photographing condition one by one, and the photographing condition setting becomes extremely easy. A helical scan of the next stage 503 is performed under such imaging conditions. Therefore, the photographing result achieves the highest priority target and the next priority target.

  FIG. 7 shows a display example of imaging condition candidates and default DLP extracted with the input of the highest priority target. It is assumed that DLP = 100 mGycm is input as the highest priority target. For this highest priority target, shooting condition candidates whose default DLP is close to that are automatically extracted and displayed together with the default DLP.

  Here, the default DLP value is 120 mGycm. Examples of scan parameters that constitute the imaging conditions include scan time, beam thickness, helical pitch, data acquisition mode (data acq. Mode), and image slice thickness. , Image interval, tube current (auto mA), tube voltage (kV), tilt angle (tilt), field of view (FOV), and total scan time (total scan time) are displayed.

  When the default DLP is reduced to 100 mGycm in accordance with the highest priority target for such a photographing condition candidate, the photographing condition candidate is automatically corrected accordingly, and the optimum photographing condition as shown in FIG. 8 is obtained.

  FIG. 9 shows a display example when two shooting condition candidates are extracted. It is assumed that DLP = 100 mGycm is input as the highest priority target. Two shooting condition candidates whose default DLP is close to the highest priority target are automatically extracted and displayed together with the default DLP. These are primary candidates.

  The default DLP is all 120 mGycm. When the default DLP is reduced to 100 mGycm in accordance with the highest priority target for these photographing condition candidates, the photographing condition candidates are automatically corrected accordingly, and the photographing conditions as shown in FIG. 10 are displayed. These are secondary candidates.

  One of these secondary candidates is automatically selected according to the next priority target, and the optimum photographing condition is obtained. When the speed is designated as the next priority target, the secondary candidate A is selected, and when the IQ is designated, the secondary candidate B is selected.

It is a block diagram of an X-ray CT apparatus. It is a figure which shows the structure of a X-ray detector. It is a figure which shows the structure of a X-ray irradiation / detection apparatus. It is a figure which shows the relationship between a X-ray irradiation / detection apparatus and object. It is a flowchart which shows operation | movement of a X-ray CT apparatus. It is a flowchart which shows operation | movement of a X-ray CT apparatus. It is a figure which shows the example of a display of imaging condition candidates. It is a figure which shows the example of a display of optimal imaging conditions. It is a figure which shows the example of a display of imaging condition candidates. It is a figure which shows the example of a display of imaging condition candidates.

Explanation of symbols

2 Scanning gantry 4 Imaging table 6 Operation console 20 X-ray tube

Claims (16)

An imaging condition setting method for an X-ray CT apparatus that performs imaging by helical scanning,
Various shooting conditions are tabulated in advance,
Extracting imaging condition candidates from the table according to the patient's designated child, imaging region, imaging length, and top priority target, and displaying the patient's exposure dose under the imaging condition candidates,
Allowing the user to adjust the exposure dose,
The imaging conditions are confirmed by performing correction according to the adjustment of the exposure dose to the imaging condition candidates.
An imaging condition setting method characterized by that. The highest priority target is exposure dose,
The imaging condition setting method according to claim 1, wherein: The highest priority target is any one of exposure dose, image quality, and imaging speed.
The imaging condition setting method according to claim 1, wherein: The exposure dose is expressed in DLP.
The imaging condition setting method according to claim 2 or claim 3, characterized in that: If there are a plurality of candidates for the shooting conditions, the shooting conditions are determined based on the next priority target specified by the user.
The imaging condition setting method according to any one of claims 1 to 4, wherein: The next priority target is different from the highest priority target among exposure dose, image quality and imaging speed.
The imaging condition setting method according to claim 5, wherein: The tabled shooting conditions are shooting conditions based on results.
The imaging condition setting method according to any one of claims 1 to 6, wherein: The tabled imaging conditions are imaging conditions based on simulation.
The imaging condition setting method according to any one of claims 1 to 6, wherein: An X-ray CT apparatus that performs imaging by helical scanning,
Storage means for storing various photographing conditions tabulated in advance;
A display that extracts the imaging condition candidates from the table according to the patient's child, the imaging region, the imaging length, and the highest priority target specified by the user and displays the exposure dose of the patient under the imaging condition candidates Means,
Adjusting means for allowing the user to adjust the exposure dose;
Confirming means for confirming the imaging conditions by performing correction according to the adjustment of the exposure dose to the imaging condition candidates;
An X-ray CT apparatus comprising: The highest priority target is exposure dose,
The X-ray CT apparatus according to claim 9. The highest priority target is any one of exposure dose, image quality, and imaging speed.
The X-ray CT apparatus according to claim 9. The exposure dose is expressed in DLP.
The X-ray CT apparatus according to claim 10 or 11, wherein The determining means determines the shooting condition based on a next priority target designated by the user when there are a plurality of candidates for the shooting condition;
13. The X-ray CT apparatus according to claim 9, wherein the X-ray CT apparatus is any one of claims 9 to 12. The next priority target is different from the highest priority target among exposure dose, image quality and imaging speed.
The X-ray CT apparatus according to claim 13. The tabled shooting conditions are shooting conditions based on results.
15. The X-ray CT apparatus according to claim 9, wherein the X-ray CT apparatus is any one of claims 9 to 14. The tabled imaging conditions are imaging conditions based on simulation.
15. The X-ray CT apparatus according to claim 9, wherein the X-ray CT apparatus is any one of claims 9 to 14.

Images